LM5037

RAMP

CLK + LEB

CLK

Vin

Current

Sense

CS

Q1

Q2

Vin

SLOPE

PROPORTIONAL

TO Vin

RAMP

COMP

Gate

Drive

1V

CLK

LM5037

LM5037

SNVS578D – NOVEMBER 2008 – REVISED MAY 2015

www.ti.com

Device Functional Modes (continued)

Figure 18. Feed-Forward Voltage Mode Configuration

7.4.4 Current Mode Control

The LM5037 device can be configured in current mode control by applying the primary current signal into the

RAMP pin. One way to achieve this is shown in Figure 19, which depicts a simplified push-pull converter. The

primary current is sensed using a sense resistor and the current information is then filtered and applied to the

RAMP pin consists of the primary current information from the CS pin plus an additional ramp for slope

Figure 19. Current Mode Configuration

Current mode control inherently provides line voltage feed-forward, cycle-by-cycle current limiting and ease of

loop compensation as it removes the additional pole due to output inductor. Also, in push-pull and full-bridge

converters, current mode control inherently balances volt-second product in both the phases by varying the duty

cycle as needed to terminate the cycle at the same peak current for each output phase. For duty cycles greater

than 50% (25% for each phase), peak current mode controlled circuits are subject to sub-harmonic oscillation.

20

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